Changing a motor switch and pulley

[MMUK]

I can't help feeling some mixed standards here MMUK

One minute you are saying
"IMHO, anyone who runs any form of machinery without one [RCD] is an idiot and an accident waiting to happen"

And elsewhere you are advocating single pole switch of a motor?

Bob

Single pole switching is perfectly acceptable and common practise in the majority of domestically available equipment. Combined with an RCD protected circuit, it's as safe as DP switching.

 

[n0legs]

Aren't RCDs obligatory in the UK?

Unfortunately not. Although any low voltage (under 1000vAC) circuit installed from 2001 onwards must be protected by an RCD as defined by BS7671 16th Edition onwards.

Incorrect.
The 17th edition makes specific mention of non-RCD protected circuits.
The 16th edition stated that sockets likely/reasonably expected to feed outside equipment should be protected by a 30mA RCD (actually I believe it was in the 15th edition). There was other guidance offered regarding their use for other applications and areas in which their use would be of benefit.
The 16th edition also mentioned the use of 100mA RCD protection for installations of TT supply type/design. This would obviously RCD protect all circuits in this type of installation. This is not really relevant in this occasion but highlights one install type/method where an RCD has to be used, I will not confuse this any further.
If you have evidence to support the "from 2001 onwards" claim, please point me in the direction of it as I seemed to have missed it.

However the use of an RCD/RCCD/RCBO greatly reduces the chance and level of electrocution. They are an extremely valuable, from a safety point of view, piece of equipment.
It is my opinion that if possible regardless of the age installation, they be installed. Granted they may cause some instances of nuisance tripping in the early days following their installation, but this is only highlighting pre-existing faults in the installation or equipment being used. These faults can be rectified.

For the OP. I have nothing to offer in the way of a solution for your issue, but I know whose advice I would follow when it comes to all things motors.

 

[HOJ]

I could get a new switch but that would completely ruin the aesthetics of the machine which I am unwilling to do.

I have an idea, use the existing original start/stop switch to act as a remote control on the contactor coil of a new, appropriate starter?

 

[Myfordman]

I reckon that is a good ploy. The remote starter can then have an appropriate thermal overload relay fitted to protect the motor. I favour the Toolstation DOL starter and overload combos available for 30 quid inc free delivery.

 

[memzey]

I might be a bit confused here but if I lined them up like that wouldn't the old switch still have more current running through it than it can handle?

 

[Myfordman]

No - that is the whole point, the old switch would only control a new, higher rated, possibly better protected switch hidden away inside/round the back etc.

Bob

Currently I am on holiday in France but can do a diagram if it is needed once I've got home and done the chores that will have piled up whilst I've been away.

 

[memzey]

So let me check I understand please:

- power would go to the isolator
- the isolator would go to the new (hidden somewhere) switch
- the new stealth switch would be connected to the motor and my old switch
- somehow my old switch would actuate the new switch
- the new switch would send current to my new 3hp sp motor

Have I got that about right? Bob - could you send me a link to the appropriate item in toolstation please? Would wiring it up for remote actuation in this way be a fairly straightforward thing to do?

 

[HOJ]

Principally thats is correct.

I will let Bob work out the details for you, but in a nutshell the existing switch buttons are wired in parallel with the
normally open, start button contacts and in series with the normally closed, stop button contacts, on the new
contactor, so just controlling the coil load, in effect carrying no current at all.

Theoretically, just need to run a 3 core + Earth cable from one to the other to make it work.

Its a system I use in my workshop to control my dust extractors remotely.

 

[Myfordman]

Tell you what Memzey, HOJ has elegantly described the wiring and you could look in the toolstation cat for what you think are the correct parts whilst I'm finishing off my holiday, post it here and then I'll take a look and see if I agree.
Not being funny but in that way hopefully you will learn a bit for the future too and build some confidence.
Whenever I asked my Dad about something he would always say - go and look it up and come and tell me what you found and we will talk about it. I learned so much more than if the solution was handed to me on a plate!

Bob

 

[dzj]

If you have to buy a new starter/ relay, you might as well get a new start/stop switch with a higher amp rating
and just replace the existing one.